The present invention relates generally to edge card connectors, and more particularly to circuit card connectors which utilize flexible circuitry as the contacts of the connector and which have an improved card engagement means.
Connectors are well known in the art which provide a connection between a primary circuit board, or "motherboard" and a secondary circuit board or "daughterboard." The connections between these two printed circuit boards typically occur along an edge the secondary circuit board, and hence such secondary circuit boards are commonly referred to in the art as edge cards.
Such circuit connectors typically include an insulative housing having a printed circuit card-receiving slot extending lengthwise within the connector, and a plurality of flexible conductive contacts which are located on opposing sides of the card-receiving slot. These contacts are typically stamped and formed. In an effort to further reduce the size of electronic components, connectors have been reduced in size and the "pitch" of connectors, i.e., the spacing between the connector contacts, has become smaller. The stamping and forming manufacturing process imposes limitations on the pitch which occurs between the contacts and therefore limits the number of circuits which the connector may accommodate. Currently, minimum pitches of about 0.5 mm are obtainable using stamped and formed contacts. This minimum pitch limits the amount of circuits for such a connector.
It has been found that using flexible circuitry for edge card connectors provides numerous advantages. First, much smaller pitches may be utilized, such as on the order of about 0.3 mm. This reduced pitch permits an even greater reduction in the size of the connectors. Second, flexible circuitry provides certain benefits to signal performance, especially with high speed signals. For example, by using conventional coplanar, microstrip or stripline configurations that are readily achievable with flexible circuitry, faster signal rise times and higher signal frequencies may be accomplished. Through the control of the dielectric materials, material thicknesses and circuit positioning parameters, it is possible to achieve improved impedance matching, lower propagation delays as well as a reduction in reflection and crosstalk.
Flexible circuitry has been incorporated in some edge card connectors, such as those shown in U.S. Pat. No. 3,614,707 issued Oct. 19, 1971 and U.S. Pat. No. 5,427,533 issued Jan. 27, 1995. Both of these connectors have a formed connector housing with a longitudinal slot and a length of flexible circuitry extending over the connector slot such that the flexible circuitry depends into the connector slot. The user inserts the circuit card into the connector slot and forces the circuit card to the bottom of the slot, forcing the edge of the circuit card against the flexible film circuitry. Repeated insertions and removals of the circuit card may impart detrimental stress to the contacts on the flexible circuitry. Additionally, these connectors require springs of complex shape behind the flexible circuitry to ensure reliable contact with the circuit card which leads to increased manufacturing costs.
The present invention is therefore directed to a circuit card connector utilizing flexible circuitry which avoids the imposition of detrimental stress on the flexible circuitry and which provides a reliable circuit card-engaging means to apply a reliable contact force to the circuit card.
One object of the present invention is to provide an improved circuit card connector which utilizes flexible circuitry as the connector contacts and which utilizes an improved circuit card-engagement assembly.
Another object of the present invention is to provide a circuit card connector having two opposing end portions formed from an insulative material and a circuit card engaging assembly supported between the connector end portions, wherein the circuit card engaging assembly includes opposing, spaced-apart spring members which extend lengthwise between the connector end portions and which support the flexible circuitry thereon, the contact spring members being movably mounted upon fulcrums such that upon insertion of the circuit card into the connector, an insertion edge of the circuit card impinges upon portions of the contact spring members which act as cam surfaces to thereby cause the contact spring members to move about their associated fulcrums into engagement with the contacts of the circuit card.
Yet another object of the present invention is to provide an improved circuit card connector which applies reliable contact forces to a circuit card inserted therein, the connector including a circuit card-engaging assembly having two opposing, spring members separated by an intervening space, the space defining an entrance portion of a card-receiving slot of the connector, the spring members having upwardly extending spring arm portions and downwardly extending leg portions, the spring members engaging fulcrums which extend lengthwise along the connector and which support the spring members at locations between the spring arm and leg portions.
Still another object of the present invention is to provide an electrical connector having a spring-biased circuit card-engaging assembly, wherein the card-engaging assembly includes a cradle spring having two fulcrums formed thereon, the fulcrums supporting a pair of contact springs on opposite sides of a circuit card-receiving slot of the connector, the contact springs having leg portions extending below the fulcrums and arm portions extending above the fulcrums, the contact springs being movable about their associated fulcrum points under urging of the circuit card when the circuit card is inserted into the connector, such that when the circuit card impinges upon the contact spring leg portions, the contact spring arm portions are urged to move into contact with opposing sides of the circuit card to thereby exert a card contact force normal to the circuit card contacts.
Yet still a further object of the present invention is to provide a high speed, high density electrical connector which has a relatively low circuit card insertion force and that includes a circuit card-engaging assembly which reliably engages the circuit card without the need for an external connector actuating mechanism, the circuit card-engaging assembly having a preload or biasing force applied thereto which biases the card-engaging into a operative position which readily receives the circuit card.